force-inline push_bytes; gets us on par with write_blob/old

cs@devvm:[~/src/neon-work-2]: cargo bench -p utils --bench write_blob
    Finished bench [optimized + debuginfo] target(s) in 0.22s
     Running benches/write_blob.rs (target/release/deps/write_blob-f10f94bd2a09aa2a)
Gnuplot not found, using plotters backend
write_blob/old          time:   [17.859 ns 18.089 ns 18.279 ns]
Found 2 outliers among 100 measurements (2.00%)
  2 (2.00%) low severe
write_blob/pr-5004-writer
                        time:   [17.886 ns 18.040 ns 18.221 ns]
Found 4 outliers among 100 measurements (4.00%)
  1 (1.00%) low mild
  3 (3.00%) high mild
write_blob/pr-4994-nopagecache
                        time:   [6.5882 ns 6.6204 ns 6.6529 ns]
Found 8 outliers among 100 measurements (8.00%)
  8 (8.00%) high mild

libs/utils/benches/write_blob.rs

@@ -210,6 +210,7 @@ mod pr5004 {
                         ephemeral_file,
                     })
                 }
+                #[inline(always)]
                 fn push_bytes(&mut self, src: &[u8]) -> Result<(), io::Error> {
                     let mut src_remaining = src;
                     while !src_remaining.is_empty() {

pageserver/src/tenant/ephemeral_file.rs

@@ -228,6 +228,7 @@ impl BlobWriter for EphemeralFile {
                     ephemeral_file,
                 })
             }
+            #[inline(always)]
             fn push_bytes(&mut self, src: &[u8]) -> Result<(), io::Error> {
                 let mut src_remaining = src;
                 while !src_remaining.is_empty() {